Gas turbines are typically constant-volume machines. At operating speed, they draw a constant volume of air through their compressor section. If the air is more dense, the same volume will contain a higher mass, so the turbine draws a higher mass flow. Cooling the air makes it denser, so the turbine runs with a higher mass flow and produces more power. In some environments, however, the air is too cold and needs to be warmed up for use by the turbine. In yet another application, the air is too close to freezing temperatures while simultaneously high in humidity, and must be warmed to reduce the risk of bellmouth icing.
The coils can be used to either cool or heat the air. When cooling, each coil is also referred to as a cooling coil. When heating, it may be referred to as a heating coil.
Gas turbine air inlet systems have employed systems to affect the temperature of the air before being conveyed to the turbine. Typically, these systems utilize coils downstream of the filtration system. Cooling coils cool the air sometimes to a temperature below the dew point of the air and will produce almost completely saturated air. Downstream of the cooling coils are systems that prevent the condensate from the coils entering the air as droplets, which is known as carry-over. Heating coils warm the air, reducing its relative humidity.
Air intake systems for gas turbines often have a non-symmetrical transition outlet from the air intake to the air flow duct that leads to the power plant. Improvements are desired.